Accuracy of the ice test in the diagnosis of myasthenia gravis in patients with ptosis.

INTRODUCTION

Several studies have reported high diagnostic sensitivity and specificity for the ice test in myasthenia gravis. All of the studies employed a case-control design, in which the diagnosis was already known at the time of the test for both patients and controls, leading to case selection bias. This suggests that the available literature substantially overestimates the diagnostic utility of these tests.

METHODS

A retrospective cohort study without selection bias was performed to examine the sensitivity and specificity of the ice test. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the ice test were determined by means of a 2 × 2 table.

RESULTS

The ice test has a sensitivity of 0.92 (95% CI 0.62-1.00), specificity of 0.79 (95% CI 0.56-1.00), PPV of 0.73 (95% CI 0.48-0.90), and NPV of 0.94 (95% CI 0.70-1.00).

CONCLUSIONS

Due to its high negative predictive value the ice test is still a reliable and useful bed-side test.